Production of asbestos products

ABSTRACT

Asbestos yarn having superior strength and uniformity is produced in a continuous process by disposing a plurality of stationary nozzles fed with asbestos dispersion within a coagulating bath to form a plurality of individual strands. The strands are continuously pulled through the coagulating bath away from the nozzles and are substantially elongated during the initial stages of progressive coagulation. The individual strands are then combined, removed from the bath and passed through a zone of low tension wherein the final stages of coagulation can take place; whereafter the combined strands can be withdrawn as a single end under tension, for example by pot spinning.

[ Apr. 23, 1974 United States Patent [191 Trainor et al. I

[ PRODUCTION OF ASBESTOS PRODUCTS [75] Inventors: James T. Trainor,Shelton; John F.

2/1961 Wilke et al.

11/1969 Wilke et a].

1/1972 Donaldson et al........

7/1972 Orzechowski et al.

m I e k a v O N 9 6 9 l. 7 8 l. 3 5 3 Primary Examiner-Jay H. Woo

Attorney, Agent, or Firm-Gary, Juettner, Pigott & Cullinan [22] Filed:'Sept. 24, 1971 [211 App]. No.: 183,327

Related US. Application Data Continuation-in-part of Ser. No. 856,716,Sept. 10, 1969, abandoned.

[57] ABSTRACT Asbestos yarn having superior strength and uniformity isproduced in a continuous process by disposing a plurality of stationarynozzles fed with asbestos dispersion within a coagulating bath to form aplurality of individual strands. The strands are continuously pulledthrough the coagulating bath away from the nozzles and are substantiallyelongated during the initial stages 8M M 6 8 H/S 7 0 5 1 8 2 O loo D ,5.00 1F 810 5 HMUW; 76121 523,8 4. 3 0 4 0 1 1 .4 4 6 M m2 m n .c r n a n.e H m L C l0 5 m n U IF U Hwm w 55 of progressive coagulation. Theindividual strands are References Cited then combined, removed from thebath and passed UNITED STATES PATENTS through a zone of low tensionwherein the final stages of coagulation can take place; whereafter thecombined strands can be withdrawn as' a-single end under tension, forexample by pot spinning.

mgrm1nme 23 :974 3,806; 572

sum 2 OF 2 1 PRODUCTION OF ASBESTOS PRODUCTS CROSS REFERENCE Thisapplication is a continuation-in-part of our copending application Ser.No. 856,716, filed Sept. 10, 1969, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to improvements in aprocess for producing asbestos products from an asbestos dispersion andmore particularly to a process wherein the dispersion is fed through astationary orifice disposed within a coagulating bath to produce acontinuous as-' bestos strand.

Various recent proposals have been made relating to the production ofasbestos products from an asbestos dispersion. The development of aneconomical commercial liquid or wet process is important in order toeliminate many potential health hazards inherrent in exposure ofpersonnel to asbestos dust generated in the conventional dry processingof asbestos.

The patents to Wilke et al. 2,972,221 and Novak et al. 3,453,818disclose the production of yarn from an asbestos dispersion by extrudingthe dispersion through a stationary nozzle into a coagulating bath. InWilke et al., the dispersion is immediately coagulated and removed forfurther processing. In Novak et al., the extrudate is somewhat stretchedduring coagulation by flowing the coagulating liquid away from theextrusion nozzle. The use of liquid flow to elongate the extruded strandis unsatisfactory, however, because a nonuniform flow of coagulatingliquid will produce an uneven strand, and the degree of elongationcannot be sufficiently controlled. Another drawback of these prior artmethods is that the resulting wet strand or yarn is normally too weak topermit continuous collection in a package suitable for subsequenttextile processing. Textile collection methods require the applicationof tension to the wet yarn, which the yarns of Wilke and Novak could nottolerate.

It is therefore desirable to provide a high speed method of producingasbestos yarn having sufficient wet strength to enable collection undertension, such as by pot spinning. Since the strength of the yarn isgreatly dependent upon proper alignment of the asbestos fibers, it isalso desirable that the fibers in the wet yarn be aligned in a directionparallel to the axis of the yarn. This result is not easily achieved bythe aforesaid prior art methods. Fine c'ut yarns produced by thesemethods are too weak and are non-uniform. Heavier cut yarns have toolarge a cross section to permit complete penetration of coagulant withina reasonable time (cut yards 100 per pound). As a result, the heavieryarn must be produced at lower speeds and proper fiber alignment is notachieved. In addition, since asbestos dispersions are non-uniform andcontain relatively large unopened fiber bundles, the strands produced bythese methods contain undesirable irregularities or weak spots.

A later Wilke patent 3,475,894 attempted to overcome the above problemsby abandoning the use of stationary nozzles in favor of driven rollers.Aprimary drawback of this method is that defects, such as splints,clots, rock, etc., are forced into the extrudate and causeirregularities and weak spots. In addition, this method does not achievemaximum fiber alignment in the wet coagulated product.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the presentinvention, the above shortcomings are overcome by providing a high speedmethod of and apparatus for producing a wet yarn. having a high degreeof fiber alignment and strength. The superior product is achieved by (i)flowing asbestos dispersion through a plurality of confined nozzlesdisposed within a coagulating bath, in order to produce a plurality ofspaced strands; (ii) exerting a positive and constant tractive force onthe individual strands during progressive coagulation thereof in orderto uniformly elongate the strands in excess of 300 percent andpreferably at least 400 percent, which results in maximum fiberalignment and maximum coagulant penetration in each strand; (iii)passing the wet strands through a zone of little or no tension untilcoagulation is complete; (iv) combining the individual strands into asingle yarn in the absence of tension; and (v) withdrawing the multiplyyarn under tension, preferably by pot spinning.

Multi-ply yarns produced by the above method exhibit substantiallygreater tensile strength in comparison with a single strand of the samecut and may be produced and collected at much higher speeds and over awider range of cuts. Fiber orientation and coagulant penetration areoptimized by the controlled drawing and stretching of a group ofrelatively fine strands during the initial stages of coagulation; thestrands are then combined in the final stages of coagulation in the formof a multi-ply yarn having a tensile strength greatly in excess of asingle strand of the same cut, thereby enabling further immediateprocessing under tension,

such as pot spinning.

THE DRAWINGS FIG. 1 is a perspective view of the apparatus employed inconnection with the presently described process; and

FIG. 2 is an elevational view, partly in section, of the apparatus shownin FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The process of the presentinvention utilizes asbestos dispersions such as those described in U.S.Pat. Nos. 2,626,213 and 2,772,157. The raw asbestos, typicallychrysotile fiber, is dispersed into the form of aqueous colloid with theaddition of a suitable dispersant. One type of a satisfactory dispersantis a fatty acid soap added in an amount of about 15 percent to 35percent by weight, although any of the other known dispersants may beemployed if capable of being chemically solidified or precipitated intowater insoluble compounds.

The asbestos dispersion is prepared in a mixer of the type that producesminimum shearing action and therefore minimum loss of fiber length. Aconventional hydrapulper employed in paper making or other vesselequipped with vertical cylindrical mixing bars is suitable for thispurpose. As described in U.S. Pat. No. 3,035,698, the dispersion is alsopreferably filtered or otherwise refined to remove as much foreignmatter, splints and large fiber bundles as possible and adjusted to afiber content of from about 0.5 percent to about 10 percent, althoughthe preferred fiber content is in the order of about 2 percent.

Although not required or necessary to the process, suitable binders orother additives may be incorporated into the dispersion prior toextrusion, as determined by special properties that may be required inthe final product. In addition, other organic or inorganic fibers may beadded,-as well as water soluble dyes.

As shown in the Figures, the dispersion is fed under low hydrostatichead to a plurality of confined orifice nozzles disposed in acoagulating bath, and the formed dispersion issuing into the bath israpidly pulled away or drawn from the nozzles in the form of a pluralityof individual strands as coagulation progresses. A container ofdispersion is 'held by a stand 12 above the area of extrusion and feedsvia one or more tubes 14 into secondary containers 16 mounted forvertical adjustment on the stand. The secondary containers 16 may thusbe vertically adjusted to regulate the amount of head at the point ofextrusion. A plurality. of tubes 18 extend generally downward from thesecondary containers, and each terminates in an extrusion nozzle 20. ltshould be noted that separate feeding of each of the nozzles isimportant in order to prevent the longer asbestos fibers from cloggingbetween adjacent nozzles, and also to aid in orientation of the fiberslongitudinally of the respective strands.

The nozzles 20 are immersed in a coagulating bath contained by anelongate vessel 22, and the drawing of the strands 24 is accomplished insubstantially a horizontal plane, with a plurality of individual strands24 being drawn through and away from the nozzles and within the bathduring progressive coagulation. Horizontal drawing is important in thatelongation or stretch of the strands maybe accurately and uniformlycontrolled, and the strands 24 are supported equally along their lengthWithin the bath during progressive coagulation.

The nozzles 20 are located along a common transverse line and aretapered toward their ends. The taper-ed conf guration of the nozzles hasbeen found to significantly improve fiber orientation and hence strengthof the strand. The outlet orifices of the nozzles are circular and, arepreferably equisizcd, with a diameter of from about 0.06 to 0.120 inchesand preferably in the order of about 0.09 inches. Smaller orifice sizesmay not be employed because of clogging problems, while larger orificesizes do not impart the desired degree of fiber orientation to theextrudate and require excessive elongation to achieve a fine cut strand.Thus,

' the size of the orifice may not be varied greatly and is heldrelatively constant, irrespective of the desired size or cut of thefinal product. The number of nozzles is critical to the extent that atleast three and preferably four or more should be employed to attain thedesired strength characteristics in the resulting yarn. To obtainvarious cuts or sizes of yarn ends, from three to fifteen to twenty ormore nozzles may be employed.

As described, the dispersion emanates from the tapered nozzles directlyinto the coagulating bath in the form of a plurality of spaced strands24. The bath may comprise an aqueous solution containing any of theknown coagulants, such as bior trivalent salts of a metal in weightconcentrations of from about 1 to 25 percent, depending on the type andamount of dispersant employed. Means may alsobe provided to slightlyagitate the bath and to circulate fresh coagulant as the availablesupply is depleted. In this manner, the polyvalent metal ions react withand precipitate the dispersant, thereby causing the dispersion to bebroken and the fibers to become frictionally interlocked and bondedtogether in aligned fashion within a matrix of water insoluble soap.

Means are provided for pulling the strands away from the nozzles and forsubstantially stretching the individual strands to a constant andcontrolled degree during the initial stages of progressive coagulation.A pair of spaced cylindrical Godet rolls 26 and 28 are mounted forrotation beyond the end of the coagulating bath remote from the pointsof strand withdrawal. The rolls 26 and 28 may be ridged on their outersurfaces to prevent slippage with the first roll 26 being locatedslightly above the level of the bath to allow some clearance be tweenthe strands 24 and the end of the vessel 22. A rod 30 or other suitablebearing surface may be located at the exit end of the bath transverse tothe strands 24 in order to prevent undue friction thereon beforecoagulation is completed. The second roll 28 is mounted below and in arearwardly spaced relationship from the first roll 26. Alternatively,the second roll 28 may be replaced by a stationary rod 32. i

The Godet rolls 26 and 28 are both driven by a suitable motor 29 at thesame surface speed and in the same'direction as the direction of strandwithdrawal.

The individual strands 24 are united or combined into a single yarn 24at the exit end of the bath, and the multi-ply yarn is wrapped over andpartially around the first Godet roll 26 and then over the second roll28 and continuously around both rolls for several wraps. The free end ofthe yarn 24' is then fed downward under tension tangentially from thefirst roll 26 directly into the funnel 34 of a spinning pct 36, as willbe hereinafter more fully described.

An important feature of the present invention is the degree of drawingand stretching that is achieved on the partially coagulated individualstrands 24 between the nozzles 20 and the first Godet roll 26. Thehydrostatic head on the viscous dispersion is maintained at a very lowlevel, while the Godet rolls 26 and 28 rotate together at a relativelyhigh speed. The net result is that the dispersion is uniformly pulledunder a constant tractive force from the nozzles and substantiallyelongated during progressive coagulation. The tapering of the nozzlesand the pulling action on the strand serves toinitially align thecolloidal fibrils parallel to the axis of filament formation. Thecoagulant in the bath then fixes the fibers in aligned position as thestrands are rapidly elongated, which causes increasingly greater surfacearea to be exposed to the coagulant and maintains the fibers in alignedposition. In order to achieve complete penetration of coagulant, each ofthe strands is elongated at least to about lOOcut, although the strandsmay, if desired, be elongated in excess of 600 cut.

Inorder to achieve rapid and complete penetration of the coagulant intothe strands and to maintain the fibers in alignment for optimumstrength, itzhas been found to be essential to provide a stretch orelongation factor on the strand in the bath in excess of 300 percent,and preferably in excess of 350 percent to 400 percent. Heretofore, ithad not been appreciated or known that stretch factors of this magnitudecould be achieved utilizing a dispersion containing only about 2 percentsolids and maintain extrusion continuity suit- .able for a commercialprocess. By combining a positive and constant tractive force on thestrands with a low head on the dispersion, we achieve substantiallycomplete and rapid penetration of coagulant while greatly improvingtensile strength.

The Godet rolls 26 and 28 (or the roll 26 and rod 32) serve severalimportant functions. As mentioned, the rolls exert a constant andpositive tractive force on the strands 24 during progressive coagulationin the space between the nozzles and roll 26, thereby resulting inmaximum strand uniformity and strength. In addition, once the combinedstrands or multiply yarn is laid on the roll 26, the rolls, since theyrotate at the same surface speed, cause little or no tension to beexerted on the newly formed and vulnerable yarn and therefore provide aquiescent or low tension zone within which the final stages ofcoagulation can take place. The dwell time of the multiply yarn on therolls is sufficient to allow complete penetration of the coagulant; thenumber of wraps taken around the rolls is appropriately adjusted toprovide the penetration time required. The Godet rolls 26 and 28, or theroll 26 and rod 32, also serve to slightly flex the yarn 24' during thefinal stages of coagulation and thus facilitate penetration of thecoagulant into the center of the strand. The Godet rolls also serve toprevent bunching of the yarn and maintain the yarn in its stretched orelongated form.

As mentioned previously, the size or cut of the individual strands andhence the cut of the final yarn is regulated primarily by adjusting thehead on the dispersion and by changing the speed of the Godet rolls,without making substantial changes in size of the nozzle orifice aspreviously discussed. The nozzle orifice must be maintained at arelatively large size as compared to conventional synthetic extrusionprocesses because of the non-uniformity peculiar to asbestosdispersions. In addition to colloidal fibrils, such dispersions normallycontain larger unopened fibers and splints which would clog a nozzlehaving an orifice less than 0.06 inches in diameter. The unexpectedability to achieve high stretch ratios simultaneously on a plurality offilaments thus'compensates for the disability to decrease nozzle orificesize.

The yarn 24' is fed from the first Godet roll 26 directly into thefunnel-shaped inlet 34 of a spinning pot 36, which comprises an upwardlyopen cylindrical container 38 rotatably driven by a suitable motor 40 ata speed in the order of 5,000 to 6,000 rpm. The funnelis reciprocatedvertically along the rotation axis of the pot such that the yarn 24 isslightly twisted and uniformly collected along the side of the pot.Since the centrifugal force within the spinning pot causes consid-'erable tension to be exerted on the wet yarn, it is important that theyarn be completely coagulated, which is assured by the steps previouslydescribed. A fraction of the tension from the spinning pot istransferred to the last wrap of yarn around the Godet rolls, therebyslightly flattening the yarn against the surfaces of the rolls. In thismanner, final penetration of the coagulant into the yarn is expeditedand the yarn is conditioned for spinning. The use of the rod 32 insteadof the second Godet roll 28 is beneficial in maximizing penetrationbecause the yarn slides across the rod and is deflected or flexed at anacute angle.

A further important feature of the present invention is the merger ofthe coagulated strands 24 into a single yarn 24' in a zone of lowtension and before significant tension is applied. Any irregularities ordefects in the individual strands due to unavoidable non-uniformities inthe dispersion are compensated for by the strength of the other strandsin the group, thereby greatly increasing the overall strength of theyarn and decreasing the likelihood of breakage.

The cured yarn coming off the roll 26 to the spinning pot 36 issubstantially non-elastic and has a moisture content in excess ofpercent and typically about percent. By virtue of the present invention,however, the multi-ply yarn also has a tensile strength in excess of 2oz. and therefore can withstand the tension exerted by pot spinning athigh speeds. The high strength of the wet yarn and rapid collectiontherefore allow for production rates easily in excess of 150 feet perminute, and at the same time the yarn is collected in a convenientpackage for subsequent processing pursuant to standard textiletechniques.

The spinning process causes from about two to five turns per inch to beimparted to the yarn, and also causes a majority of the excess water tobe removed. The tension on the yarn between the Godet roll 26 and thepot 36 may vary, and the tension decreases as the quantity of yarn inthe pot increases. This varying tension, however, is not imparted to theuncoagulated strands because of the presence of the Godet rolls 26 and28, which serve to isolate the spinning stage tension from the stage ofinitial progressive coagulation and also from the low tension zone wherecoagulation is completed.

In order to illustrate the degree of improvement that the present methodprovides over the method of Novak et a]. U.S. Pat. No. 3,453,818,comparative tests were conducted on the apparatus herein described. Theyarn was not collected in the spinning pot, however, but was withdrawnfor testing. In comparing a single ply yarn of 70 cut with a four plyyarn of 70 cut (280 out per ply), it was found that the untwisted wettensile strength of the single ply was about 1 to 2 ounces, whereas thefour ply yarn of the same cut had a tensile strength of about 4 to 6ounces. The production rates of the single strand yarn could not exceed40 to 60 feet per minute because of frequent breakage problems, whilethe production rate of the four-ply yarn of the same cut could easilyexceed 150 to 200 feet per minute.

From the foregoing, it will be appreciated that the present inventionallows for the rapid production of asbestos yarn in a commerciallyfeasible manner, since the. yarn must have a tensile strength in excessof two or three ounces to enable collection in a spinning pot, and sinceproduction speeds of less than feet per minute would not be economicallyfeasible. The present invention thus allows for production at strengthsand speeds in excess of these minimum criteria without detriment to thequality of the final product.

Having thus described the invention, what is claimed 1. A method forproducing asbestos yarn from an asbestos dispersion that is subject tocoagulation, comprising the steps of forming the dispersion into aplurality of individual strands, subjecting the strands to progressivecoagulation while uniformly drawing the strands into an elongate form,continuously passing said strands through a zone of low tension untilcoagulation thereof is substantially complete, merging the strands intoa multi-ply yarn, and continuously withdrawing said strands undertension from said zone of low tension, said zone of low tension servingto isolate the steps of yarn withdrawal from the step of strandformation.

2. The method of claim 1 wherein the strands are elongated duringprogressive coagulation in excess of 300 percent 3. The method of claim1 wherein the strands are flexed in said zone of low tension.

4. A method for producing a uniform asbestos yarn of high tensilestrength from a non-homogeneous asbestos dispersion, wherein thedispersion is passed through a nozzle into a coagulating bath to form acontinuous strand, comprising the steps of flowing the dispersion underhydrostatic head through a plurality of nozzles within a coagulatingbath to produce a plurality of individual spaced strands, exerting aconstant and uniform pulling force on the progressively coagulatingstrands sufficient to elongate said strands in excess of 300 percent,continuously passing said elongated strands through a zone of lowtension until coagulation thereof is substantially complete whilemaintaining said strands in their elongate form and while merging saidstrands together substantially in the absence of tension thereon, andcontinuously withdrawing the coagulated strands under tension by potspinning from said zone of low tension.

'5. The method of claim 4 wherein the step of passing said strandsthrough a zone of low tension comprises wrapping said strands severaltimes around a pair of spaced rolls rotating at the same surface speed.

6. The method of claim 4 wherein the nozzles have an orifice of about0.09 inches and said yarn is withdrawn in excess of feet per minute.

1. A method for producing asbestos yarn from an asbestos dispersion thatis subject to coagulation, comprising the steps of forming thedispersion into a plurality of individual strands, subjecting thestrands to progressive coagulation while uniformly drawing the strandsinto an elongate form, continuously passing said strands through a zoneof low tension until coagulation thereof is substantially complete,merging the strands into a multi-ply yarn, and continuously withdrawingsaid strands under tension from said zone of low tension, said zone oflow tension serving to isolate the steps of yarn withdrawal from thestep of strand formation.
 2. The method of claim 1 wherein the strandsare elongated during progressive coagulation in excess of 300 percent.3. The method of claim 1 wherein the strands are flexed in said zone oflow tension.
 4. A method for producing a uniform asbestos yarn of hightensile strength from a non-homogeneous asbestos dispersion, wherein thedispersion is passed through a nozzle into a coagulating bath to form acontinuous strand, comprising the steps of flowing the dispersion underhydrostatic head through a plurality of nozzles within a coagulatingbath to produce a plurality of individual spaced strands, exerting aconstant and uniform pulling force on the progressively coagulatingstrands sufficient to elongate said strands in excess of 300 percent,continuously passing said elongated strands through a zone of lowtension until coagulation thereof is substantially complete whilemaintaining said strands in their elongate form and while merging saidstrands together substantially in the absence of tension thereon, andcontinuously withdrawing the coagulated strands under tension by potspinning from said zone of low tension.
 5. The method of claim 4 whereinthe step of passing said strands through a zone of low tension compriseswrapping said strands several times around a pair of spaced rollsrotating at the same surface speed.
 6. The method of claim 4 wherein thenozzles have an orifice of about 0.09 inches and said yarn is withdrawnin excess of 150 feet per minute.